Liquid-phase processing of hydrophilic features on a silicon wafer

The four distinct stages of silicon wafer processing which are relevant to features such as trenches, vias, and topology are: (1) feature wetting, (2) chemical transport into and (3) out of the feature, and (4) feature drying. The present investigation is focused on hydrophilic surfaces. The time scales on which the mechanisms dominating these stages occur have been established. These time scales, while different, are nevertheless significantly shorter than the process time scale. In addition to that, the drying stage is analyzed under ''worst case scenario'' assuming that all the water in the feature evaporates within the feature leaving a solid silica particle. It is shown that this particle is several orders of magnitude smaller than a particle whose size may have a detrimental effect on the device. The findings exemplify the advantages of spray technology by demonstrating the importance of (i) fresh liquid at the feature top and (ii) rapid exchange of chemicals.